London has been battered by 50mph winds that have felled trees and caused travel chaos. Powerful gusts swept across the capital as the Met Office issued a yellow "be aware" weather alert for most of the country.

The Mayor of London's plan for a 'Boris Island' were dealt a blow today as the shadow transport secretary ruled out the idea.

Theresa Villiers said Boris Johnson's idea of building an airport in the Thames Estuary as an alternative to expansion at Heathrow was "not Conservative policy". She also said Mr Johnson was "independent" from the national party.

Mr Johnson wants to build up to six runways on an island in the estuary two miles off Sheerness in Kent. A feasibility study is currently being conducted by Doug Oakervee, chair of the Crossrail project.

But Mrs Villiers said: "It is not the Conservative policy to build an airport in the estuary. Boris is independent of the Conservatives on this issue."

The split comes after Mr Johnson signalled that he might not stand as Mayor for a second term prompting speculation he still harboured dreams of becoming Prime Minister.

The Standard last month revealed that Mr Johnson might not stand for a second term as Mayor — and would be ready to serve as Prime Minister.

In an interview he said "nothing is excluded", fuelling speculation that Mr Johnson will use City Hall as a springboard for an attempt to take Downing Street. The move triggered an electrifying rivalry with David Cameron at the top of the Conservative party, with the mayor openly defying the Tory leader by supporting the idea of an "earned amnesty" for illegal immigrants.

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The Mayor has also shown his ambition for power beyond City Hall by setting out plans for new academies and calling for Latin and Greek to be reintroduced in the national curriculum.

Local government expert Tony Travers said: "However hard they both say there is no power struggle it's very easy to infer there is. Boris is a very clever and ambitious man and it would be more surprising if he weren't after the job. I can't believe David Cameron will be entirely unaware of the threat

"On this issue Boris is keeping the London voters happy by talking about an airport out in Kent, but it's no so easy for the national party. This is about election politics."

The Tories share the mayor's view that the Heathrow third runway but support alternative plans for a high-speed rail link from London to Birmingham, Manchester and Leeds, with trains running at up to 190mph.

Mrs Villiers said: "We oppose a third runway at Heathrow. We want to make Heathrow better not bigger. [But] we are not looking at the option of a new airport in the Thames Estuary."

The Mayor's office does not believe the rail link will be enough and insists there needs to be more aviation provision in the capital.

He is considering factors such as the London Array wind farm which is currently under construction as well as concerns about wildlife.

The Mayor's director of transport policy Kulveer Ranger said: "We accept it's not the policy of the national Tory party but Boris has to looks at what affects London and act in Londoners interests.

"He has said he will not support a third runway so there needs to be an alternative as well as high speed rail links and this is one alternative that is being considered."